Gas recovery system for oxygen blast converters

ABSTRACT

A feedback pipe is connected to the outlet and inlet sides of a storage blower directing unburned gas from an oxygen blast converter to a storage tank. Alternatively, the unburned gas is discharged to the atmosphere. Control valves moving in contrary directions are coupled to a single controller for maintaining the pressure in the storage delivery pipe constant regardless of whether unburned gas is discharged to the atmosphere or directed to the storage tank.

United States Patent Inventor Motoaki l-lirao I Hyogo, Japan Appl. No. 14,906

Filed Feb. 27, 1970 Patented Nov. 2, 1971 Assignee Kawasaki Jukogyo Kabushiki Kaisha Hyogo, Japan GAS RECOVERY SYSTEM FOR OXYGEN BLAST CONVERTERS 5 Claims, 3 Drawing Figs.

U.S. Cl 266/35, 75/60 Int. Cl. C21c 5/42 Field of Search 266/34 R, 35, 36 P; 75/60 [56] References Cited UNITED STATES PATENTS 3,118,759 1/1964 Okaniwa et al. 75/60 3,333,839 8/1967 Maehara et al 266/35 Primary Examiner-Gerald A. Dost A'tmrney-Sughrue, Rothwell, Mion, Zinn & MacPeak ABSTRACT: A feedback pipe is connected to the outlet and inlet sides of a storage blower directing unburned gas from an oxygen blast converter to a storage tank. Alternatively, the unburned gas is discharged to the atmosphere. Control valves moving in contrary directions are coupled to a single controller for maintaining the pressure in the storage delivery pipe constant regardless of whether unburned gas is discharged to the atmosphere or directed to the storage tank.

GAS RECOVERY SYSTEM FOR OXYGEN BLAST CONVERTERS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas recovery system for oxygen blast converters, and more particularly to an improved recovery system for storing the unbumt gas from the converter after passage through a cooling and dust-removing device.

2. Description of the Prior Art Generally, oxygen blast converters are periodically operated for periods of 30 to 50 minutes including l to 25 minutes for refining and time for charging of the hot metal and discharging of the steel. At the first stage and the last stage of the refining operation, the air or carbon monoxide gas in the cooling and dust-removing device are purged by combustion with introduced air to form a gas layer therein. Accordingly, the exhaust gas at the first and last stage of the refining operation includes very small amounts of carbon monoxide gas and is of no utility value. At the stage of refining operation between the above-mentioned first stage and the last stage, unbumt carbon monoxide gas of 70 to 80 percent concentration can be obtained in a cooling device by controlling the pressure in the cooling device near the atmospheric pressure with a valve disposed at the inlet of the suction blower to prevent the leakage of the exhaust gas and introduction of the external gas. Since the gas having the high concentration of the carbon monoxide has utility value, the gas is often stored for other utilization.

With the above-described storing device, it is known to provide a switching valve at the outlet of the suction blower to selectively guide the gas into the exhaust stack or into the storage gas duct. But such a storing system is disadvantageous in the following points: 7

First, since the gas pressure of the recovered gas at the storing side is several hundred mm. in a water gauge above the atmospheric pressure while the pressure of the exhaust stack is of course almost atmospheric pressure, the delivery pressure of the suction blower abruptly fluctuates whenever the switching valve is switched. Accordingly, the gas flow controlling system fails to control the gas flow and the gas pressure in the cooling device is not controlled properly. In order to solve this problem or disadvantage, sometimes a secondary butterfly valve for pressure control is disposed in the exhaust stack. But such a system is still disadvantageous when switching the gas flow to exhaust into the atmosphere from movement to the storage tank at a pressure of as high as several hundred mm. in a water gauge. The larger the pressure difference is, the more difficult the controlling is and the worse the followup characteristics of control becomes. This is, therefore, not a perfect way to solve the above problem.

Second, since the gas discharged into the atmosphere is after it is raised in pressure, the power for raising the pressure constitutes a loss of energy. This is a great disadvantage in an industrial apparatus.

, SUMMARY OF THE INVENTION The present invention provides an improved recovery system for storing the gas in which pressure control is stably performed and the power is efficiently used.

The recovery system in accordance with the present invention is provided with a storing blower for forcing the gas into a storage tank downstream of the suction blower for sucking out the gas. The feedback flow of the gas from the outlet of the storage blower to the inlet and thereof is controlled to obtain a better control of the gas pressure in the system. There is also provided a controlling valve downstream of the storing blower to make the switching of the flow to exhaust and storage tank easier and more stable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic view of the system in accordance with the present invention,

FIG. 2 is a detailed view of the main portion of the system in accordance with the present invention, and

FIG. 3 is a graph showing the efiects of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring to FIG. 1, the reference character 1 denotes a converter 1 which receives an oxygen lance 2. A hood 3 directs gas to a cooling device 4 and a dust remover 5. The suction blower is indicated at 6 and a storing and exhausting switch valve 7 selectively directs gas to a discharging stack at 8 or storage delivery pipe 9 carrying storage blower 10. A feedback pipe ll, and gas storage tank 12 are provided. The pressure difference between the gas in the hood 3 and the atmosphere is detected by a low-pressure detector 13, and the detected signal is transmitted to the automatic control device 14 to control the angle of the flow control valve 15 so as to make the pressure in the hood 3 nearly equal to the atmospheric pressure. The exhaust gas from the converter 1 is sucked into the hood, cooled and dust-removed, and introduced to the suction blower 6 without being burnt. The purifled gas discharged out of the suction blower 6 is led out to the atmosphere through the discharging stack 8, when the concentration of the carbon monoxide therein is relatively low, and introduced to the storage delivery pipe 9 by switching the switch valve 7 when the concentration of the carbon monoxide therein is relatively high. The gas introduced into the storage delivery pipe 9 has its pressure raised to several hundred mm. as measured by a water gauge with the storage blower 10 and introduced into the storage tank 12. The pressure difierence between the gas in the storage pipe 9 and the atmosphere is detected by the pressure difference detector 16. The gas pressure in the storage pipe 9 is maintained constant by the flow control valve 18 disposed at the outlet end of the storage blower l0 and the flow control valve 19 disposed at the feedback pipe 11, both being controlled by an automatic control device 17 connected therewith. The constant pressure in the storing pipe 9 is a positive pressure less than several tens of mm. as measured by a water gauge above the atmospheric pressure required to make it possible to discharge the gas out of the discharging stack 8 into the atmosphere.

Referring to FIG. 2, showing the details of the main portion of the system shown in FIG. 1, where the same elements are indicated by the same reference numerals, the gas exhausted from the suction blower 6 is directed into the discharging stack 8 by opening the valve 20 in the stack 8 and closing the valve'2l in the pipe 9, and is directed into the storage delivery pipe 9 and further into the storage tank I2 by closing valve 20 in the discharging stack 8 and opening valve 21 in the storage delivery pipe 9. Accordingly, the valve 20 in the discharging stack 8 and the valve 21 in the storage pipe 9 are made to operate in opposition at the same time by a remote controlling device manually or automatically operated.

It is important to maintain the pressure constant in the pipe 9 whether gas is stored or not, in order to prevent the pressure at the outlet of the suction blower 6 from fluctuating greatly when switching the flow of gas. The gas pressure in the storage delivery pipe 9 is controlled by the pressure control valve 18 at the outlet of the storage blower I0 and secondarily controlled by the control valve 19 in the feedback pipe 11.

The gas flow to be directed through the feedback pipe 11 is in accordance with the characteristic of the storing blower 10. That is, in the case there is a surging limit for the blower, it is economical from the viewpoint of consumption of electric power to control the quantity of the gas flow through the feedback pipe up the surging limit of the blower. In the case of using a storage blower having no surging limit, almost all the range of the gas flow from faint gas flow up to the maximum gas flow can be obtainable by controlling the control valve at the outlet of the storage blower. In this case the gas flow in the feedback pipe 11 can be reduced down to a faint flow, low enough to prevent the harmful rising of temperature of the gas in the storage blower. Since, during discharging, there is no gas flow in the storage delivery pipe 9, some feedback of the gas into the pipe is required to control the gas pressure in the pipe 9. In operation for the above-described gas behavior, the controlling valves 18 and 19 operate in a contrary way, that is, when one of the two is opened, the other is closed.

FIG. 3 shows the relation of the quantity of the stored gas W with the quantity of the gas B flowing through the storing blower. When there is no stored gas, that is, W is zero, a gas quantity equal to r flows through the feedback pipe only. At the right-hand end point of the graph of FIG. 3, the quantity of the stored gas is equal to that of the gas through the storage blower and, accordingly, there is no gas flowing through the feedback pipe 11, with the valve 19 in the feedback pipe 11 closed completely. In the intermediate state, a part of the gas blown through the storing blower indicated by r' in the graph is fed back through feedback pipe 11 and the residual gas indicated by w is introduced into the storing tank 12.

The invention has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the scope of the invention as described hereinabove and as defined in the appended claims.

What is claimed is:

l. A gas recovery system for storing unburnt gas from an oxygen blast converter comprising:

a. a hood for guiding the exhaust gas from the converter,

b. a suction blower connected to one end of said hood for exhausting gas from the converter,

c. a discharging stack connected to said suction blower for discharging the exhaust gas into the atmosphere,

d. a storage delivery pipe connected to said suction blower for directing the exhaust gas into a storage tank,

e. switching means disposed at the outlet end of said suction blower for selectively switching gas flow into said discharging stack or said storage delivery pipe,

f. a storage blower disposed at an intermediate position within said storage delivery pipe, and

g. a feedback pipe connected at one end thereof with the outlet of said storage blower and connected at the other end thereof with the inlet of said storage blower.

2. A gas recovery system as claimed in claim 1 wherein said feedback pipe is provided therein with a gas flow control valve for controlling the feedback gas flow therethrough.

3. A gas recovery system as claimed in claim 2 further including a gas flow control valve disposed at the outlet of said storage blower.

4. A gas recovery system as claimed in claim 3 wherein: the gas flow control valve at the outlet of said storage blower and said gas flow control valve in said feedback pipe are coupled to a single controller for simultaneous movement in contrary directions.

5. A gas recovery system as claimed in claim 4 wherein said single controller is connected to a detector which detects the difference in pressure between the atmosphere and the gas in said storage delivery pipe; whereby the gas pressure in said storage delivery pipe is maintained at a constant level by controlling both said valves. 

2. A gas recovery system as claimed in claim 1 wherein said feedback pipe is provided therein with a gas flow control valve for controlling the feedback gas flow therethrough.
 3. A gas recovery system as claimed in claim 2 further including a gas flow control valve disposed at the outlet of said storage blower.
 4. A gas recovery system as claimed in claim 3 wherein: the gas flow control valve at the outlet of said storage blower and said gas flow control valve in said feedback pipe are coupled to a single controller for simultaneous movement in contrary directions.
 5. A gas recoveRy system as claimed in claim 4 wherein said single controller is connected to a detector which detects the difference in pressure between the atmosphere and the gas in said storage delivery pipe; whereby the gas pressure in said storage delivery pipe is maintained at a constant level by controlling both said valves. 